Hybrid aircraft carriers (2 Viewers)

[EwenS]

I'm trying to communicate that the hybrids survived because they had a lot of AA. IIRC, Shokaku and Zuikaku (purpose built carriers) did have a lot of AA like you predicted. Yet their AA wasn't able to drive off dive bombers targeting Zuikaku. As impractical as hybrids design was, credit where credit is due. Somehow Ise and Hyuga's ineffective guns did drive off a f-ton of aerial bombs and torpedoes. Doesn't that count for something? It's frankly weird that no one is willing to recognize this.

By the way, random info here: there's a source on Japanese Wikipedia which claims both hybrids used radar guidance for ship targeting. But I don't have any sources as to its FCS. My guess is it used manual targeting against aircraft.

AA armaments in Oct 1944. So very little difference between I & H and Zuikaku, the largest carrier in Ozawa's force in Oct 1944.

Ise & Hyuga
The 14in guns were equipped with a limited number of sanshiki-dan / sankaidan incendiary shrapnel rounds, some of which were fired when the attackers were still at long range.
16x5in AA (8x2)
104 x25mm (31x3, 11x1)
6x28 barrelled unguided rocket launchers firing incendiary shrapnel shells.

Zuikaku
16x5in AA (8x2)
96x25mm (21x3, 33x1)
6x28 barrelled unguided rocket launchers firing incendiary shrapnel shells.

As for the 25mm this is from the Navweaps site:-
"The Japanese considered the 25 mm gun to be an excellent weapon, but it did not compare well to either the Bofors 40 mm or to the Oerlikon 20 mm weapons used by the Allies.

The magazines for the Type 96 held only 15 rounds, so frequent stoppages for change outs were required. By 1945, these weapons fired projectiles too light and too short ranged to effectively engage the heavier and faster US aircraft then in service."

For the TF38 aircrews in Oct 1944, the carriers were the primary target against which the bulk of their effort was directed initially. Chitose was left sinking after strike 1 and Zuiho & Zuikaku badly damaged. Strike 2 left the Chiyoda crippled and ablaze, while Zuikaku and Zuiho managed to drive off many of the aircraft from this strike attacking them. Strike 3 saw Zuikaku finally succumb to 6 torpedo hits and Zuiho to torpedo & bomb hits. It is only in the late afternoon that Ise came under a heavy attack in strike 4 with many near misses being made. For there to be "near misses" the USN aircraft must have been pressing home their attacks, not being put off by the weight of fire coming from the Ise.. The heavy AA fire from I & H, when they were in close proximity to the carriers during at least part of the day failed to save any of them. So for all the weight of AA armament, very little "driving off" was done by any IJN ship and certainly not by Ise & Hyuga.

I & H seem to have led a charmed life that day and the next. Both aircraft (late in the day) and submarine torpedos aimed at them missed altogether, while most of the bombs aimed at them also missed, albeit some close enough to cause some relatively minor damage.

By 1944 large Japanese warships were equipped with

Type 21 - an air search set
Type 13 - air search set. HYuga picked up the first USN strike on this set at 105 miles.
Type 22 - surface search set. It could generally not be used for fire control as its range error was too great.
Neither did the IJN use its radars for fighter control. But having the radars at least gives the gunners warning of an impending attack and the direction from which it is coming which is always useful.

Edit. Ozawa sending I & H ahead of the carriers on the night of 24/25 Oct was simply another part of the deception to draw TF38 north away from guarding Leyte Gulf. Their plan was to draw out the US fast battleships into a night action, which usually favoured the Japanese. However I & H accompanied by 4 destroyers were spotted by a radar equipped Hellcats on search missions around 0200-0230 some 80 miles north of TF38, with the rest of Ozawa's force 40 miles north of that. By 0700 on 25th the entire IJN force was back together never having engaged the US surface action TF34 assembled to engage it.

Admiral Lee was ordered to form his battle line (TF34) drawn from ships of TF 38 and sail about 10 miles ahead of the carriers That comprised the 16in battleships Iowa, New Jersey, Massachusetts, South Dakota, Washington & Alabama, 2 CA, 3 CL and 14 destroyers. More than enough to overpower the IJN "Vanguard Force" had they encountered each other.

 

[AerialTorpedoDude69]

E Ewan thanks again, it's super useful to see the exact count of guns. But I believe you are wrong that near misses are evidence of a failure of AA. After all, both the Franklin and Bunker Hill IIRC were put out of commission during engagements by smaller numbers of Japanese aircraft. Sometimes planes drop their bombs and hit their target. A near miss means they were disrupted enough by AA to miss their target.

"Luck is what happens when preparation meets opportunity." - Seneca

According to Japanese sources, the hybrids' commander's AA scheme deterred attacks. But there are few details other than that it was the density of AA that was effective. Additionally, there was an October 1944 refit that added additional guns and weaponry to the useless flight deck. Unfortunately, Japanese Wikipedia did not go into details. And the official info from the 1943 remodeling does not include these additions.

But because both ships escaped serious and determined attacks relatively unscathed suggests more than just luck was involved. The 14-inch guns' san-shiki rounds and its multi-rocket AA system probably only had a psychological impact on USN and USAAF pilots, but this was probably enough to disrupt the kind of coordinated attacks which proved fatal to so many other Japanese carriers.

 

[EwenS]

E Ewan thanks again, it's super useful to see the exact count of guns. But I believe you are wrong that near misses are evidence of a failure of AA. After all, both the Franklin and Bunker Hill IIRC were put out of commission during engagements by smaller numbers of Japanese aircraft. Sometimes planes drop their bombs and hit their target. A near miss means they were disrupted enough by AA to miss their target.

No it doesn't. There are a variety of factors that could lead to a near miss. Pilot not taking sufficient account of wind direction / strength when aiming. Ship manoeuvering. To name but 2.

According to Japanese sources, the hybrids' commander's AA scheme deterred attacks. But there are few details other than that it was the density of AA that was effective. Additionally, there was an October 1944 refit that added additional guns and weaponry to the useless flight deck. Unfortunately, Japanese Wikipedia did not go into details. And the official info from the 1943 remodeling does not include these additions.

The figures I gave were their final AA fits from about mid-1944. Zuikaku had her AA fit increased to the figures given in a refit in July 1944 which included the addition of the rocket launchers. I & H had their AA augmented around the same time.
The singles on the I & H were fitted on the flight deck, as were some, but not all those on Zuikaku.

But because both ships escaped serious and determined attacks relatively unscathed suggests more than just luck was involved. The 14-inch guns' san-shiki rounds and its multi-rocket AA system probably only had a psychological impact on USN and USAAF pilots, but this was probably enough to disrupt the kind of coordinated attacks which proved fatal to so many other Japanese carriers.

The sanshiki shells were only of use at long range as aircraft approached. And the 14in guns only had a rate of fire of 2 rpm. Aircraft cover a lot of ground in that time.

The 28 round rocket launchers had been developed as a rush programme in June 1944, using both an existing mount (from the triple 25mm) and director (Type 95). A practical rate of fire was 16-20 rockets per minute despite a higher theoretical figure. Reloading time 3-5 minutes. With time fuzes their range was 1,000-1,500m. Its biggest problem was that the mount could not trained and elevated rapidly enough and that the sight was inadequate for high speed targets.

The carriers Zuikaku, Junyo, Unryu & Amagi were equipped with 6 of these in July / Aug 1944 followed by Katsuragi, Ise & Hyuga in Sept / Oct. At least one source states that Zuiho had also received 6 mounts by the time of her loss.

So it was another altogether ineffective weapon, just as the RN had found with its UP Projectors in 1940/41.

 

[AerialTorpedoDude69]

No it doesn't. There are a variety of factors that could lead to a near miss. Pilot not taking sufficient account of wind direction / strength when aiming. Ship manoeuvering. To name but 2.

Let's just say that the effect of massed anti-aircraft cannons and rockets (even ineffective ones) are a few of many factors that could throw off a bombing run?

Here's what the commander said about how he dodged so many bombs:

In the anti-aircraft battle during this period, a barrage firing method conceived by Commander Chikao Matsuda proved effective, reportedly downing 30 to 70 enemy aircraft. Additionally, a maneuver to evade bombs by cruising at normal speed and then making a sharp turn as dive bombers entered their attack run was highly successful. This maneuver caused the target to slip out of sight from the perspective of attacking aircraft. Dive bombers, once committed to their descent, could not make major adjustments to their trajectory and had to release their heavy bombs before being able to climb again. As a result, many bombs missed their targets.

In other words, they'd wait until the dive bomber committed to a run and then they'd make a hard right turn.

I don't know whether it was the guns blazing, the divine wind, or what-have-you, but something happened to make so many aircraft miss their targets. The commander of the ships attributed it to AA and helmsmanship. But it's also clear that radar played a major factor. Luck too maybe? But there are just too many attacks on two different ships to say it was purely luck.

I don't believe the hybrids' flight-deck guns are included in the tally of guns you've provided. There were additional guns added over the summer in 1944 according to Japanese Wikipedia (which your numbers I think included). But then more guns were added to the flight deck in October, just before Leyte and Taiwan Air Battle. Here's the source for this.

EDIT: I believe you are right about the number of AA cannons and that the 1944 refit was the final refit.


Here's a translation of the relevant section:

The 634th Air Group was formed as their air unit, and efforts were made to equip both ships with part of the group's aircraft and conduct training and maintenance. However, due to the impact of the Battle of the Philippine Sea, the aircraft were redirected to the Philippines, leaving the Ise-class effectively functioning as battleships during Operation Sho-Go. During the Battle off Cape Engaño, Ise and Hyuga reportedly downed numerous U.S. aircraft with barrage fire. They also utilized a bomb evasion technique proposed by Rear Admiral Chikao Matsuda, which helped them avoid direct hits.

Prior to this sortie, the ships underwent minor modifications, abandoning plans for aircraft deployment. Instead, machine guns were installed on their flight decks for anti-aircraft defense, and they were equipped with 12 cm 28-barrel rocket launchers.

In other words, they were updated AGAIN just before Leyte, with additional guns on the flight deck.

//EDIT:

Japanese Wikipedia has the 1944 refit as having the following number of 25mm AA guns:

• 31 25mm triple mounts,
• 11 single guns

Comparing the pre-1945 schematic to the 1943 schematic, it looks like 14 guns were added to the flight deck, but they do not use the same nomenclature as the 25mm single or triple mounts, except on two emplacements added to the rear of the ship. These might be something like Type 3 13.2mm heavy machine guns or 25mm single mounts.
//EDIT


A pre-1944 schematic shows all of the AA gun emplacements, but it doesn't differentiate between single and triple mounts. But near as I can tell, the flight-deck guns are not included in the final tally of guns.

But the exact number of guns is beside the main point that I believe it was the AA (and radar) which allowed for the hybrids to survive for so long.

You know a lot more about this subject by far, but drawing on your excellent understanding of the subject, you must certainly agree that AA and radar were crucial components in surviving aerial bombing attacks. It seems we only disagree on the effectiveness of the "barrage" system employed by the hybrids. More to the point, if a ship has the AA firepower on paper and it's successful at surviving aerial barrage, then didn't those AA guns account for something?

I'm reminded of the 2015 NBA championship where the Warriors were accused of being "lucky" when they beat out the Grizzlies and the Rockets. On paper, yeah, they looked awesome. They had won a blistering number of games in the regular season. Like close to 70. Is that luck or something more than luck? Lucky is such a subjective value, yeah, sure, I didn't play well in a pickup game, but that's because the other guys got lucky. Never mind the fact that they were better prepared and younger. And taller. Those are all advantages only on paper.

 

[Warspite63]

Re: turret removal from Ise and Hyuga: the loss of the 2 aft turrets had less of an impact than it might appear. When the ships were rebuilt in the 30's, it was not possible to increase the elevation for these turrets, as the hulls lacked the depth. The other 4 turrets were upgraded. Also, Hyuga only lost Turret 6 in her bastardization conversion to hybrid battleship/carrier: Turret 5 had been removed following an accidental explosion in ....1942, I think

I still agree that it was a waste of time and effort though

 

[don4331]

While Hyuga had turret 5 destroyed in a breech failure, all the other turrets on H & I could elevate to 33* (range >33,000 yds.) <just not the 43* of turrets 1 thru 4>. Yet HMS Warspite remains in contention for the longest hit on a moving target (~26,000yds) - and her turrets could only elevate to 30* (Note: At 30* HMS Warspite range is actually 29,000 yds., so she wasn't quite at elevation stops (assuming 4crh round, if Warspite was firing 6crh rounds range is even longer)). Therefore, turrets 5&6 not being able to elevate to 43*, really wasn't that much of a restriction.

On the other hand: The conversion to air transports only took 9 months; what other solution would have provided IJN with 44 additional a/c (11 recon/11 attack each) on a 25kn platform with >9k nm range?

Perfect is the enemy of good enough.​

 

[Shortround6]

On the other hand: The conversion to air transports only took 9 months; what other solution would have provided IJN with 44 additional a/c (11 recon/11 attack each) on a 25kn platform with >9k nm range?

does anybody know the amount of aviation fuel and/or the magazine stowage for aviation ordnance?
Both things that need major revisions to the ship if done in large volumes. But for the 'historical' mission of a one shot mission for the 12-15 D4Y Suisei bombers just 12-15 500kg bombs needed to be stored and perhaps a few dozen 250kg bombs for the Aichi E16A float planes? This is a far cry from the scores (hundreds?) of tons of bombs/torpedoed carried by medium size carrier. Even the Furious carried around 20,000 gallons of fuel, which was rather pathetic.

 

[AerialTorpedoDude69]

They were each capable of launching 22 D4Y dive bombers each, but the only time they catapulted aircraft in combat was during the Air Battle for Taiwan and they lost most of the nine which they were equipped with. It's mentioned on Wikipedia that there was a lack of trained pilots, but the larger issue was that the Suisei could only be produced in limited numbers due to the special alloying process used to produce its 1,400 HP engine.

 

[EwenS]

does anybody know the amount of aviation fuel and/or the magazine stowage for aviation ordnance?
Both things that need major revisions to the ship if done in large volumes. But for the 'historical' mission of a one shot mission for the 12-15 D4Y Suisei bombers just 12-15 500kg bombs needed to be stored and perhaps a few dozen 250kg bombs for the Aichi E16A float planes? This is a far cry from the scores (hundreds?) of tons of bombs/torpedoed carried by medium size carrier.

Petrol storage was arranged in tanks with a volume of 111 cubic metres (24,400 Imp Gal, 29,300 US Gal) in the former No 6 turret magazine, within the armoured citadel with pump & control rooms above. Its position was seem as "advantageous" compared to Japanese carriers.

Bombs were carried in the former No 5 turret magazine. Enough for three full strikes.
44xNo 50 bombs of 500kg (1,100lbs)
22 No 25 bombs of 250kg (550lbs)

Both rated as Armour Piercing in IJN terminology. There was a bomb hoist to lift then direct to the flight deck.

Even the Furious carried around 20,000 gallons of fuel, which was rather pathetic.

Context is everything.
The decision to convert Furious was taken in 1920 when the only full deck carrier experience was with the the Argus (completed Sept 1918) and some trials in the only partially completed Eagle in 1920. Design work began in July 1920 and was completed in early 1921, with her hull being stripped to main deck level before the Washington Conference even began. Various mixes of aircraft were suggested but eventually it was built around six 6 aircraft flights, for a total of 36, with the types operated when she entered service in 1925 being:-

1 Fighter Flight - Fairey Flycatcher (Nimrod / Osprey from 1932)
2 Torpedo flights - Blackburn Dart / Ripon to 1933
2 Spotter flights - Blackburn Blackburn / Avro Bison (Fairey IIIF from 1929)
1 Recce flight - Fairey IIID (Fairey IIIF from 1927

Not a gas guzzling 1,500-2,000hp engine in sight! In fact none over 600hp before 1930.

Designed for 24,000 Imp Gal bulk storage, the RN had worries about leaks in the pipework & patrol vapour build up. So bulk storage was cut back but 2x600 gal jettisonable tanks were placed at main deck level. The thought was that the 600 gal tanks would be used to fill the aircraft and be refilled from main storage less often, resulting in less volatile petrol flowing around the pipework in the ship. In 1939 she had a bulk capacity of 20,800 gal and AIUI, still had the disposable tanks. The RN had a much healthier respect for bulk storage of petrol than the USN and the steps it took to protect that came at a cost of reduced volume all the way through WW2.

Unlike the USN, the RN had a worldwide network of bases that ships could pop into and top up in a way that the USN with its plans to crosss the Pacific in time of war could only dream of. And the RN certainly wasn't contemplating a scale of air operations anywhere near that of the USN.

They were each capable of launching 22 D4Y dive bombers each, but the only time they catapulted aircraft in combat was during the Air Battle for Taiwan and they lost most of the nine which they were equipped with. It's mentioned on Wikipedia that there was a lack of trained pilots, but the larger issue was that the Suisei could only be produced in limited numbers due to the special alloying process used to produce its 1,400 HP engine.

Only in the very early plans was the air group to consist entirely of D4Y2-Kai Model 22 Suisei (aka Judy to the Allies). This, was an aircraft to be built specially for I & H and required a strengthened fuselage and small flaps amongst other modifications to allow its use from a catapult (IJN carriers were not catapult equipped). None were available when the conversions completed in Aug 1943 and Nov 1943. As a result in early 1944 the air group was changed to operate a mix of types.

4th Carrier Division to control I & H, and the 634th Air Group to supply its aircraft were formed on 1 May 1944 with separate Judy & Paul units. There were delays producing the Judys and in its early days the unit only had 16 Pauls and 6 Judys. The lack of aircraft prevented the pair from participating in the Battle of the Philippine Sea in June 1944. The planned air group was intended to be (later reduced to just 22):-

18 Judy (+ 6 reserve) split between the two ships.
18 Paul (+ 6 reserve) split between the two ships.

On 23 June 1944 I & H embarked aircraft for the first time. Each carried 4 Judy and 6 Paul aboard for practice catapult launches. Further launches were carried out on 21 July and 31 August. 1944. Meanwhile training ashore was limited by lack of Judys and grounding of the Pauls for a period. The result was bombing training only took place 3 times in Aug.

Because I & H couldn't recover their intended Judys, 4th Carrier Division and 634th Air Group were expanded by the addition on Junyo on 10 July (36 operational + 12 reserve aircraft) and Ryuho on 10 August 36 operational + 12 reserve aircraft).

By 1 Sept 1944 while the 634th Air Group had 176 aircraft only 20 of these were catapult capable Judy for I&H and only 11 were operational plus 21 Pauls. By 1 Oct there were 17 Judy (6 operational) 18 Pauls (16 operational). By 14 Oct this was 9 &12 respectively. And the whole 634th Air Group was in a poor state of training. So when they sailed as part of Ozawa's Northern Force on 18 Oct I & H carried NO operational aircraft, and nor did they at any subsequent time. Ise had her catapults removed while undergoing repairs between 29 Oct & 8 Nov 1944. Hyuga's were removed while she was at Sasebo 7-9 Nov 1944.

For Ise & Hyuga history see Hans Lengerer's article "Ise and Hyuga: The IJN's Hybrid Battleship-Carriers" in Warship 2009

Detailed histories of their movements can be found here.

Japanese Battleships Operational Histories | Nihon Kaigun